This invention relates to a soil-displacement drill which comprises a drill pipe, a substantially cylinder-shaped portion on the lowermost end thereof and a cone-shaped point connecting to said portion, and at least one spiral rib, which spiral rib comprises a portion lying on the point and having a downwardly-extending outer side, and a portion which connects to the end of said first rib portion, lies on the cylinder-shaped portion and has an outwardly-extending top side.
Such soil-displacement drills are used for the vibration-free making of concrete piles on the ground. Due to the presence of the spiral rib, the displacement drill enters the ground as it is rotated, whereby the soil is pushed away and thus compacted around the drill opening.
The spiral rib is thus no cutting member and the displacement drill is thus not suitable for drilling very hard materials such as rocks. A cutting drill may well do so on the other hand, as it is provided on the point thereof with one or a plurality of cutting members. Said cutting members cut away the soil which is discharged, for example through the drill pipe.
A soil-displacement drill of the above-described type is known from German Utility Model No. G 79 23 274.9 in the name of the Applicant.
The soil-displacement drill according to said Utility Model comprises a single spiral rib. That side facing the point end of the spiral portion lying on the point is directed at right angle to the geometrical axis of the drill. Said point end-facing side does however merge without changing s1ope and without discontinuity, into the point end-facing side of that spiral rib portion lying on the cylinder-shaped portion.
Moreover, the succeeding windings of the single spiral rib connect sidewise to one another, on the point at least. On said point, that side facing the point end of the one winding of the spiral rib connects directly to the outer side, lying generally in parallel relationship with the geometrical drill axis, of a winding lying closer to the point end.
The soil-entering of said known displacement drill occurs relatively slowly and requires much power.
One reason for this is probably the fact that the soil particles can move in the upwards direction relative to the point exclusively by following the spiral rib, whereby they thus have to move along that side facing the point end of the spiral rib. It is clear that said soil particles have to cover thereby quite a long path for a limited upwards displacement relative to the point. With such known drills, the soil appears to be pressed-away mostly sidewise by the point. The blade-shaped portion of the spiral rib lying on the cylinder-shaped portion actually causes a displacement along a direction in parallel relationship with the geometrical axis of the drill, that is along a vertical direction, of the already sidewise-compacted soil particles, but horizontally-displaced soil particles often have to wait for a half to nearly one revolution before also being displaced along a vertical direction.
The invention has for object to provide a displacement drill which enters the soil more easily and faster than said known displacement drill.